The present invention is related to a power converter and management system for providing energy to a pulsating load.
Batteries in general and small Lithium primary batteries in particular have limitations with respect to the amount of current that can be supplied to a connected load. The current is especially limited by the internal resistance of the battery as the voltage drop across the internal resistance reduces the battery voltage significantly.
Another effect is the deterioration of the battery capacity when loaded with high current pulses. In many electronic systems (low duty cycle systems) short pulses of high current have to be delivered by the battery. In such cases it is common practice to overcome the high internal resistance of the battery by connecting a shunt capacitor in parallel to the battery or using a dedicated storage capacitor. A disadvantage is the internal leakage current of the capacitor, that will add to the supply current. Especially when electrolytic capacitors are used, this leakage can be significant. It reduces the lifetime of the battery and thus the electronic system supplied by the battery.
Examples of such systems are Wireless Communications systems based on the IEEE 802.15.4 (Zigbee) standard. These are characterized by very low duty cycles of operation which means that long periods of inactivity are followed by a short active time period in which radio communication takes place, requiring a short pulse of high supply current.
A way to overcome some of the problems associated with supplying pulsating loads is to buffer energy from the battery in an energy storage capacitor. A known system uses voltage conversion techniques to charge and discharge a buffer capacitor. However such a system cannot be used in low power consumption applications which cannot tolerate the internal and external leakage current associated with the buffer capacitor. Further the high tolerance and temperature coefficient of practical capacitors reduce the efficiency of the energy transfer of the system which negatively impacts the battery lifetime.